The elongation step in eucaryotic protein synthesis requires a soluble factor, usually designated as elongation factor 1 (EF-1), which is responsible for the attachment of aminoacyl-tRNA to ribosomes. One objective of the proposed research is to unequivocally establish the subunit structure of the heavy form of the enzyme from a variety of eucaryotic sources, including Artemia salina embryos, sea-urchin embryos, and HeLa cells. Purification of the factor from these sources and analysis of the purified factor by the techniques of protein chemistry and immunochemistry should provide a convincing answer to this problem. In embryos of Artemia salina a heavy form of EF-1 consists of at least two different subunits, one of which is functionally related to bacterial EF-Tu (eEF-Tu) and the other is analogous to bacterial EF-Ts (eEF-Ts). Essentially nothing is known about either the biosynthesis of these factors or their stoichiometric relationship to ribosomes. Quantitative analysis of the EF-1 content of the cells (or organisms) cited above by radioimmunoassay combined with measurements on the ribosome content of the aforementioned cells should yield data on the stoichiometry of the factor with respect to ribosomes. Studies on the biosynthesis of the factor in early and and late cleavage sea-urchin embryos as well as HeLa cells are proposed. These will be designed to establish whether there is a coordination between EF-1 synthesis and ribosomal protein synthesis. The biosynthesis of EF-1 and eEF-Tu will be investigated in an attempt to determine whether EF-1 is an intermediate form in the process of catalyzing aminoacyl-tRNA binding of ribosomes. The relationship between the synthesis of EF-1 and elongation factor 2 will be examined in different cells with the aim of understanding how elongation factor synthesis is coordinated. The possible role of the elongation factor or structurally related proteins in processes other than protein synthesis will be studied.